Sheathlin is a protein that exists in the enamel matrix and is also referred to as ameloblastin or amelin. Amino acid sequences of sheathlins in swine, human, bovine, mouse and rat are already known (ameloblastin derived from the rat incisor: Krebsbach P H, Lee S K, Matsuki Y, Kozack C A, Yamada K and Yamada Y, Full-length sequence, localization, and chromosomal mapping of ameloblastin. A novel tooth specific gene., J. Biol. Chem., 271: 4431-4435, 1996; amelin derived from the rat molar: Cerny R, Slaby I, Hammarstrm L and Wuitz T: A novel gene expressed in rat ameloblasts codes for proteins with cell binding domains., J. Bone Miner. Res., 11: 883-891, 1996; sheathlin derived from swine: Hu C C, Fukae M, Uchida T, Qian Q, Zhang C H, Ryu O H, Tanabe T, Yamakoshi Y, Murakami C, Dohi N, Shimizu M and Simmer J P: Sheathlin: Cloning, cDNA/polypeptide sequences, and immunolocalozation of porcine enamel sheath proteins., J. Dent. Res., 76: 648-657, 1997; sheathlins derived from human, bovine and mouse: Toyosawa S, Fujiwara T, Ooshima T, Shintani S, Sato A, Ogawa Y, Sobue S and Ijuhin N: Cloning and characterization of the human ameloblastin gene., Gene, 256: 1-11, 2000).
Further, an antibody that recognizes the sequence of the 27th to 47th amino acid residues of sheathlin (derived from rat, corresponding to SEQ ID NO: 6) has been disclosed (The Journal of Histochemistry & Cytochemistry, 45(10), 1329-1340 (1997)). However, this publication only discloses that a certain particular antibody recognizes such an amino acid sequence and does not disclose nor suggest production of a peptide having such an amino acid sequence or use of the peptide for pharmaceutical purposes and so forth.
Further, various pharmaceutical uses of a tetrapeptide derived from amelin and various pharmaceutical uses of amelin (therapeutic and prophylactic treatments of periodontal diseases, repair of tooth lesions, bonding of bone elements, promotion or induction of mineralization of hard tissues, effective uptake of an implant into the bone, improvement of biocompatibility of implant instruments etc.) have been reported (International Patent Application Unexamined Publication in Japanese (Kohyo) No. 11-510377). However, the peptide of the present invention described later, pharmaceutical use thereof and so forth have not been disclosed nor suggested.